I just wanted to confirm that both the 74" and the 80" cylinders are the same height. From what I understand the 80" is larger bore is all. I want to know if I should keep a pair of nice 74" jugs for my 80".
Thanks,
Dave

 

No Nooo...You must send those to Me, to avoid Confusion and Frustration!!!!!
Seriously, I have used them interchangeably. Good stash!

 

they would have to be bored to .060 over to use them with a std bore 80 inch piston - the stroke is different in the 74 motor verses the 80 inch motor as well

 

Thanks,
I thought they were the same height but....
Does a 74" piston have greater height than 80" to get the compression?
I would imagine so.
Thanks,
Dave

 

Good point. Longer rods, is the answer!

 

looking at the dome one could surmise the compression is different - BUT keep it around 8.5 to 1 - the reason is the Fuel is garbage today

if you have an 80 inch lower unit the compression height is different than that of the 74 inch motor pistons -- and in the interest of common parts SO you can fix it with out braking the bank keep the stuff with the parts in common - IE all 74 stuff if its a 74 all 80 stuff if its an 80 inch its cheaper trust me

 

Thanks for all the answers. My last bike was a 41FL and most all the 74" stuff was interchangeable with other gen style motors.
Dave

 

1941 was the change year for the big twin and earlier motors are restored to the later if the entire engine is re done as it is easyer to get replacements going foward

 

Both cyls the same length, piston wrist pin location on the 3 31/32" stroke 74", is lower than the 4 1/4" 80" piston.
Scott